The present invention is generally in the area of polymeric matrices containing microspheres or microcapsules for controlled release of encapsulated compounds or modification of the polymer matrix.
The use of microcapsules for controlled drug delivery or implantation of cells or other materials into a patient is well known. For example, U.S. Pat. No. 4,352,883 to Lim describes the microencapsulation of a variety of substances. U.S. Pat. No. 3,464,413 to Goldfarb et al. discloses bandages containing microcapsules which release drugs when ruptured. Similarly, the use of biocompatible, bioerodible polymeric implants, such as the devices made from polyglycolic acid, polylactic acid or polyanhydrides, are also well known. K. W. Leong et al describe the use of polyanhydride implants for controlled drug delivery in "Bioerodible polyanhydrides as drug-carrier matrices. I: Characterization, degradation, and release characteristics", J. Biomedical Mater., 19,941-955 (1985).
Outside of the controlled drug delivery area, there has been little utilization or development of microcapsule or polymeric devices for controlled release of materials embedded within the polymers. Even within the area of controlled drug delivery, it has been difficult, if not impossible, to achieve the desired release kinetics for a bioactive substance from either polymer films or microcapsules. The preferred type of release occurs relatively linearly over time ("zero order kinetics"), not irregularly as a function of variations within the polymer chains or the relative thicknesses of different portions of the device. Even with spheres of apparently uniform diameter, linear release is not obtained.
It is therefore an object of the present invention to provide a method and means for forming a polymer matrix containing a uniform distribution of microcapsules or microspheres including bioactive or other compounds.
It is another object of the present invention to provide a method and means for releasing bioactive or other compounds from a polymeric matrix at a desired rate and quantity.
It is a further object of the present invention to provide a method and means for controlled release of bioactive or other compounds from a polymer matrix which can be controlled by external stimuli such as light, temperature, or ultrasound.
It is yet another object of the present invention to provide a method and means for forming a permeable or porous polymeric membrane after the polymer is polymerized and formed into the desired shape.